A _dedicated_ 120V/15A circuit will handle a 30L-1 on SSB. A 20A circuit will handle any mode on the 30L-1 or an AL-80A or B, as well.
I agree there should be nothing else on the circuit but the amp, though.
I ran my 80A on a dedicated 15A circuit for several years because there was no convenient way to get a 240V circuit into the existing shack. The 30L-1 was on the same circuit. Obviously I only ran one amp at a time.
My current shack has 3 120V/20A circuits just for the radios and a 240V/20A circuit for the amps -again, one at a time.73,
Lon - W3LK